1. Field of the Invention
The present invention relates to apparatuses and methods to splice and terminate electrical cables. More particularly, the invention relates to several fittings capable of joining two composite core cables by the load bearing composite cores and to several fittings that can terminate or dead end the composite core cables.
2. Description of the Related Art
The blackouts in 2003 that affected the United States, Great Britain, and France have demonstrated an urgent need to update the world's power grids. An elegant and immediate solution is the replacement of existing conductors with composite core reinforced cables. An example of a composite core reinforced cable, the ACCC cable, is described in PCT Application No. PCT/US03/12520, which is incorporated by reference herein. Hereinafter, the ACCC cable will be used to represent all composite core cables. These ACCC cables provide a greatly increased ampacity. In some situations, the ACCC cable may provide a 100% increase in ampacity. Replacing antiquated cables with ACCC cables is an obvious and effective method for increasing the capabilities of the world's electrical transmission and distribution systems. To replace the outdated cables, linemen will need to install the ACCC or other composite core cables onto existing structures.
Unfortunately, current methods and devices to install these cables do not exist. To install the ACCC cables, the linemen must be able to splice the cables and attach the cables to poles or structures using dead ends. Unfortunately, existing devices and methods will not be effective.
While cable lengths for a single strand of ACCC cable may cover several thousand feet, a power grid requires several hundred or thousand miles of cable. To span these distances, the linemen must splice or couple two smaller cable spans together. The splice functions as both a mechanical junction that holds the two ends of the cables together and an electrical junction allowing the electric current to flow over or through the splice.
With the traditional aluminum conductor steel reinforced cable (ACSR), the cable is formed from a set of twisted aluminum conductors wrapped around a core of steel wires. The aluminum conductor mostly functions as the electrical conductor, while the steel core mostly functions as the load-bearing member. The aluminum conductor does carry some of the load, and the steel core does help conduct some of the electric current. To splice two ACSR cable spans, linemen use a device such as a full tension compression splice. Hubbell/Fargo Manufacturing, of Poughkeepsie, N.Y., offer these types of splices. For this device, a lineman strips the aluminum away from the steel core. A sleeve or die is placed over the end of the exposed core. The lineman leaves a small part of the steel core exposed beyond the end of the sleeve. A compression vise is used to affix the sleeve to the steel core. The sleeve and steel core from both cables are then inserted into a second tube. The tube is long enough to cover the sleeve and part of the aluminum conductor that was not stripped away. This tube is also crimped with a compression vise. These implements create compression fittings that hold both the aluminum conductor and the steel core.
The method just described works well with ACSR cables, but is ineffective with ACCC cables. First, the aluminum conductor is not a load bearing member in the ACCC cable. Thus, crimping a tube to the aluminum conductor does not hold together the composite core load-bearing members of the two cables. In addition, the exceptional crimping force used, around 60 tons psi, could crush the composite core. Thus, the methods used for ACSR cables are flawed because the methods do not provide a good mechanical coupling between the load-bearing members of the ACCC cables.
In the composites industry, composite members are often adhered together. A special glue, epoxy, or adhesive is applied to the composite and to the member being affixed to the composite. Unfortunately, several problems occur with these adhesive bonds. First, adhesives do not spread the forces applied to the bond across the entire area of the bond. Rather, forces tend to localize along one or two inches of the bond. With the incredible tensional forces on the cables (up to 60,000 pounds or more), the adhesive bonds tend to fail in successive one inch regions until the entire bond is compromised. Also, bonding to a composite member tends to apply forces to the outer fibers in the composite. Thus, as forces build, the fibers on the exterior of the composite fail, and then the bond fails also. To compensate, some composite manufacturers slice the composites lengthwise along an acute angle. Then, the two sliced composites are bonded along the slice. This bond distributes the forces along all the fibers not just those on the exterior of the composite. Unfortunately, the composite core of an ACCC cable is small. Making the slices in these cores would be extremely difficult. In addition, bonding the composites would require special tools, materials, and training beyond that a lineman currently enjoys. The use of adhesives in the field is also difficult because of environmental pollutants, such as moisture, dust, and other airborne materials, that can affect the proper mixing and setting of the adhesives.
To terminate a cable, a lineman normally installs a dead end. Similar devices and methods to the splice are used in the industry to install dead ends. Thus, the same problems mentioned above exist for dead ends also.
Thus, there exists a need for a cable splice for ACCC reinforced cables and other composite core cables, and there exists a need for a cable dead end for these composite core cables.